The possibility that the genome of the yeast Saccharomyces cerevisiae contains a homolog to the ets proto-oncogene was explored by several approaches. An oligo-nucleotide, NAK46, derived by reverse translating a conserved segment of the ets coding sequence, was shown to hybridize predominantly to a single band for four different restriction digests of yeast genomic DNA. Clones corresponding to the NAK46 sequence are being identified by hybridization to cosmid and lambda libraries, as well as filters containing a grid of clones representing 82% of the yeast genome. A phylogenetic study of 26 ets family sequences was performed using several different methods. This analysis produced a phylogenetic history of the ets gene family in the context of metazoan evolutionary radiation. A minimum of five duplication events of primordial ets genes were identified. The first three of these duplications preceded the vertebrate-invertebrate divergence, an event that occurred at least 500 million years ago. The murine GAPB` gene was found to have homology to the ets "A" region, as well as the "C" region, and possibly to be the vertebrate homolog of the Drosophila elg gene.